Dry metal etching method

ABSTRACT

A method of etching an aluminum-containing layer on a substrate is described. The method includes forming plasma from a process composition containing a halogen element, and exposing the substrate to the plasma to etch the aluminum-containing layer. The method may additionally include exposing the substrate to an oxygen-containing environment to oxidize a surface of the aluminum-containing layer and control an etch rate of the aluminum-containing layer. The method may further include forming first plasma from a process composition containing HBr and an additive gas having the chemical formula C x H y R z  (wherein R is a halogen element, x and y are equal to unity or greater, and z is equal to zero or greater), forming second plasma from a process composition containing HBr, and exposing the substrate to the first plasma and the second plasma to etch the aluminum-containing layer.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to a method for etching a metal-containing layeron a substrate.

2. Description of Related Art

In semiconductor manufacturing, metal-containing materials are commonplace and pose formidable challenges to process integration. Inparticular, improved metal etch processes are required.

SUMMARY OF THE INVENTION

Embodiments of the invention relate to a method for etching ametal-containing layer on a substrate. Additional embodiments of theinvention relate to a method for etching an aluminum-containing layer,such as aluminum, aluminum alloy, or aluminum oxide (AlO_(x)) on asubstrate.

According to one embodiment, a method for etching a metal-containinglayer on a substrate is described. The method includes disposing asubstrate having an aluminum-containing layer formed thereon in a plasmaprocessing system, forming plasma from a process composition containinga halogen element, and exposing the substrate to the plasma to etch thealuminum-containing layer. The method additionally includes exposing thesubstrate to an oxygen-containing environment to oxidize a surface ofthe aluminum-containing layer and control an etch rate of thealuminum-containing layer.

According to another embodiment, a method for etching a metal-containinglayer on a substrate is described. The method includes disposing asubstrate having an aluminum-containing layer formed thereon in a plasmaprocessing system, forming first plasma from a process compositioncontaining HBr and an additive gas having the chemical formulaC_(x)H_(y)R_(z) (wherein R is a halogen element, x and y are equal tounity or greater, and z is equal to zero or greater), and exposing thesubstrate to the first plasma to etch the aluminum-containing layer. Themethod further includes forming second plasma from a process compositioncontaining HBr, and exposing the substrate to the second plasma to etchthe aluminum-containing layer.

According to yet another embodiment, a method for etching ametal-containing layer on a substrate is described. The method includesdisposing a substrate having an aluminum-containing layer formed thereonin a plasma processing system, forming plasma from a process compositioncontaining a halogen element, applying an electrical bias to thesubstrate by coupling radio frequency (RF) power to a substrate holderupon which the substrate rests, and exposing the substrate to the plasmato etch the aluminum-containing layer. The method additionally includesachieving a target etch selectivity between the aluminum-containinglayer and a layer containing Si and O formed on the substrate byadjusting an RF power level for the electrical bias.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A through 1C illustrate a schematic representation of variousmethods for preparing a device structure on a substrate;

FIG. 2 provides a flow chart illustrating a method for etching ametal-containing layer on a substrate according to an embodiment;

FIGS. 3A through 3C illustrate a schematic representation of a procedurefor etching a metal-containing layer on a substrate according to otherembodiments;

FIG. 4 provides a flow chart illustrating a method for etching ametal-containing layer on a substrate according to another embodiment;

FIG. 5 shows a schematic representation of a plasma processing systemaccording to an embodiment;

FIG. 6 shows a schematic representation of a plasma processing systemaccording to another embodiment;

FIG. 7 shows a schematic representation of a plasma processing systemaccording to another embodiment;

FIG. 8 shows a schematic representation of a plasma processing systemaccording to another embodiment;

FIG. 9 shows a schematic representation of a plasma processing systemaccording to another embodiment;

FIG. 10 shows a schematic representation of a plasma processing systemaccording to another embodiment;

FIG. 11 shows a schematic representation of a plasma processing systemaccording to another embodiment;

FIG. 12 depicts a cross-sectional view of a plasma source in accordancewith one embodiment;

FIGS. 13A and 13B depict a cross-sectional view and bottom view of aplasma source in accordance with another embodiment; and

FIG. 14 depicts a cross-sectional view of a plasma source in accordancewith yet another embodiment.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

In the following description, for purposes of explanation and notlimitation, specific details are set forth, such as a particulargeometry of a processing system, descriptions of various components andprocesses used therein. However, it should be understood that theinvention may be practiced in other embodiments that depart from thesespecific details.

Similarly, for purposes of explanation, specific numbers, materials, andconfigurations are set forth in order to provide a thoroughunderstanding of the invention. Nevertheless, the invention may bepracticed without specific details. Furthermore, it is understood thatthe various embodiments shown in the figures are illustrativerepresentations and are not necessarily drawn to scale.

Various operations will be described as multiple discrete operations inturn, in a manner that is most helpful in understanding the invention.However, the order of description should not be construed as to implythat these operations are necessarily order dependent. In particular,these operations need not be performed in the order of presentation.Operations described may be performed in a different order than thedescribed embodiment. Various additional operations may be performedand/or described operations may be omitted in additional embodiments.

“Substrate” as used herein generically refers to the object beingprocessed in accordance with the invention. The substrate may includeany material portion or structure of a device, particularly asemiconductor or other electronics device, and may, for example, be abase substrate structure, such as a semiconductor wafer or a layer on oroverlying a base substrate structure such as a thin film. Thus,substrate is not intended to be limited to any particular basestructure, underlying layer or overlying layer, patterned orun-patterned, but rather, is contemplated to include any such layer orbase structure, and any combination of layers and/or base structures.The description below may reference particular types of substrates, butthis is for illustrative purposes only and not limitation.

As noted above in semiconductor manufacturing, metal etching continuesto pose formidable challenges for process integration. As an example,FIG. 1A provides a pictorial illustration of a first metal-containinglayer patterning scheme. Therein, a plurality of device structures 100are formed on a substrate 110 by patterning a device stack that includesa metal-containing layer (150A, 150B, 150C). The metal-containing layer(150A, 150B, 150C) may include a metal, a metal alloy, a metal oxide, ametal nitride, or a metal silicate. Accordingly, there exists the needto pattern etch the metal-containing layer (150A, 150B, 150C) whileachieving acceptable profile control and etch selectivity between themetal-containing layer and other materials on the substrate.

As another example, FIG. 1B provides a pictorial illustration of asecond metal-containing layer patterning scheme. Therein, a plurality ofdevice structures 101 are formed on a substrate 110 by preparing adielectric layer 114, such as a silicon nitride layer or a silicon oxidelayer, and filling the pattern formed in the dielectric layer 114 with ametal-containing layer (151A, 151B, 151C). The metal-containing layer(151A, 151B, 151C) may include a metal, a metal alloy, a metal oxide, ametal nitride, or a metal silicate. Accordingly, there exists the needto etch back the metal-containing layer (151A, 151B, 151C) whileachieving acceptable etch selectivity between the metal-containing layerand other materials on the substrate.

In both cases, it is important to break through any metal oxide formedat the exposed surface of the metal-containing layer, and controllablyetch the metal-containing layer. For example, in the latter, it isimportant to break through any metal oxide formed at the exposed surfaceof the metal-containing layer (151A, 151B, 151C), and controllably etchthe metal-containing layer (151A, 151B, 151C) to an etch depth rangingup to about 300 Angstrom (e.g., up to about 200 Angstrom, or rangingfrom about 50 Angstrom to about 200 Angstrom). Furthermore, it isimportant to etch the metal-containing layer (151A, 151B, 151C) withselectivity to the dielectric layer 114. Further yet, it is important toetch the metal-containing layer (151A, 151B, 151C) uniformly acrosssubstrate 110.

As illustrated in FIG. 1C, a plurality of device structures 102 areformed by filling the pattern formed in the dielectric layer 114 with ametal-containing layer (152A, 152B, 152C). During the etching of themetal-containing layer (152A, 152B, 152C), exposed metal surfaces (155A,155B, 155C) of the metal-containing layer (152A, 152B, 152C) evolvedownward, thus, forming recesses in the metal-containing layer (152A,152B, 152C). However, the evolution of the exposed metal surfaces (155A,155B, 155C) proceeds non-uniformly due to the evolution of oxygen fromexposed dielectric surface 115 as an etch byproduct of the consumptionof the dielectric layer 114 during the etching of the metal-containinglayer (152A, 152B, 152C). Differences in diffusion paths (116A, 116B,116C) of oxygen from the exposed dielectric surface 115 to variousexposed metal surfaces (155A, 155B, 155C) causes variations in theoxidation rate of these exposed metal surfaces, thus, establishing apattern dependency of the etching of the metal-containing layer (152A,152B, 152C).

Therefore, according to an embodiment, a method for etching ametal-containing layer on a substrate is illustrated in FIG. 2. Aspresented in FIG. 2, the method comprises a flow chart 200 beginning in210 with disposing a substrate having a metal-containing layer formedthereon in a plasma processing system. The metal-containing layer maycomprise a metal, a metal alloy, a metal nitride, or a metal oxide, orcombinations thereof. Further, the metal-containing layer may include analuminum-containing layer, such as aluminum, aluminum alloy, or aluminumoxide (AlO_(x)), or combinations thereof. For example, themetal-containing layer may include a bulk aluminum layer with analuminum oxide surface layer. Additionally, for example, themetal-containing layer may be utilized in a semiconductor device.Additionally yet, for example, the metal-containing layer may beintegrated in a device structure (e.g., device structure 100, 101)depicted in FIGS. 1A and 1B.

The substrate may include a bulk silicon substrate, a single crystalsilicon (doped or un-doped) substrate, a semiconductor-on-insulator(SOI) substrate, or any other semiconductor substrate containing, forexample, Si, SiC, SiGe, SiGeC, Ge, GaAs, InAs, InP, as well as otherIII/V or II/VI compound semiconductors, or any combination thereof. Thesubstrate can be of any size, for example a 200 mm (millimeter)substrate, a 300 mm substrate, or an even larger substrate.

In 220, plasma is formed from a process composition containing a halogenelement. The process composition may include a halogen element and oneor more elements selected from the group consisting of C, H, F, Cl, andBr. Additionally, the process composition may include Br and one or moreelements selected from the group consisting of C, H, F, and Cl.

The process composition may contain a fluorine-containing gas, achlorine-containing gas, a bromine-containing gas, a halide gas, or ahalomethane gas, or any combination of two or more thereof. For example,the process composition may include F₂, Cl₂, Br₂, BCl₃, NF₃, or SF₆.Additionally, for example, the process composition may include a halide,such as HF, HCl, HBr, or HI. Furthermore, for example, the processcomposition may include a halomethane, such as a mono-substitutedhalomethane (e.g., CH₃F), a di-substituted halomethane (e.g., CH₂F₂), atri-substituted halomethane (e.g., CHF₃), or a tetra-substitutedhalomethane (e.g., CF₄).

The process composition may further include an additive gas containing Cand one or more elements selected from the group consisting of H, F, Cl,Br, and I. For example, the process composition may further include ahydrocarbon (i.e., C_(x)H_(y), where x and y are equal to unity orgreater). Alternatively, for example, the process composition mayfurther include a fluorocarbon (i.e., C_(x)F_(y), where x and y areequal to unity or greater). Alternatively yet, for example, the processcomposition may further include an additive gas having the chemicalformula C_(x)H_(y)R_(z), where R is a halogen element, x and y are equalto unity or greater, and z is equal to zero or greater.

In one embodiment, when etching an aluminum-containing layer, theprocess composition may include HBr.

In another embodiment, when etching an aluminum-containing layer, theprocess composition may include HBr and an additive gas containing C andone or more elements selected from the group consisting of H, F, Cl, Br,and I.

In another embodiment, when etching an aluminum-containing layer, theprocess composition may include HBr and an additive gas having thechemical formula C_(x)H_(y)F_(z), where x, y and z are equal to unity orgreater.

In yet another embodiment, when etching an aluminum-containing layer,the process composition may include HBr and an additive gas having thechemical formula CH₃F.

In 230, the substrate is exposed to the plasma to etch themetal-containing layer. The method of etching the metal-containing layermay include preparation of an etch process recipe. The etch processrecipe may include one or more process conditions defined by one or moreprocess parameters. The one or more process conditions may beestablished by setting one or more process parameters, such as: settinga flow rate of the process composition; setting a pressure in the plasmaprocessing system; setting a first radio frequency (RF) power level fora first RF signal applied to a lower electrode within a substrate holderfor supporting and electrically biasing the substrate; setting a secondRF (or microwave) power level for a second RF signal applied to a sourceantenna or electrode opposing the lower electrode above the substrate;setting a temperature condition for the plasma processing system;setting a temperature condition for the substrate or substrate holder;setting an etch time; and/or setting an over-etch time. During themethod of etching, any one of the process parameters may be varied.

In one embodiment, the method of etching may comprise a processparameter space that includes: a chamber pressure ranging up to about1000 mtorr (millitorr) (e.g., up to about 200 mtorr, or ranging fromabout 30 to about 100 mtorr), a halogen-containing gas flow rate rangingup to about 2000 sccm (standard cubic centimeters per minute) (e.g., upto about 1000 sccm, or about 1 sccm to about 200 sccm), an optionaladditive gas flow rate ranging up to about 2000 sccm (e.g., up to about1000 sccm, or up to about 100 sccm, or up to about 10 sccm, or rangingfrom about 1 sccm to about 10 sccm), an optional noble gas (e.g., He orAr) flow rate ranging up to about 2000 sccm (e.g., up to about 1000sccm, or up to about 500 sccm), a SWP (surface wave plasma) source(e.g., element 1180 in FIG. 11) power ranging up to about 3000 W (watts)(e.g., up to about 2500 W, or ranging from about 1500 W to about 2500W), and a lower electrode (e.g., element 522 in FIG. 11) RF power levelfor electrically biasing the substrate ranging up to about 1000 W (e.g.,up to about 500 W, or up to about 200 W, or up to 100 W). Also, the SWPsource can operate at a microwave frequency, e.g., 2.48 GHz. Inaddition, the lower electrode bias frequency can range from about 0.1MHz to about 100 MHz, e.g., about 2 MHz or 13.56 MHz.

In 240, the substrate may be exposed further to an oxygen-containingenvironment to oxidize an exposed surface of the metal-containing layerand control an etch rate of the metal-containing layer. For example,when etching an aluminum-containing layer, the etch rate for aluminumoxide using an HBr-based process composition is less than the etch ratefor aluminum. Through the addition of oxygen, the etch rate for themetal-containing layer may be reduced to less than or equal to about 100Angstrom per minute (min), or less than or equal to about 50 Angstromper min. Thus, the amount of the metal-containing layer (e.g., depth orthickness) removed may be relatively more controllable. Additionally,through the addition of oxygen, the pattern deficiency noted above inFIG. 3C may be reduced or even eliminated. Herein, the inventors suspectthat oxygen addition may dilute and eradicate the pattern dependentevolution of oxygen from oxide surfaces adjacent the metal-containinglayers being etched.

The oxygen-containing environment may contain atomic oxygen, diatomicoxygen, triatomic oxygen, metastable oxygen, excited oxygen, ionizedoxygen, oxygen-containing radical, etc. The oxygen-containingenvironment may contain O, O₂, O₃, CO, CO₂, NO, N₂O, or NO₂, or anycombination of two or more thereof. The oxygen-containing environmentmay include an oxygen-containing plasma. The generation of theoxygen-containing plasma may be located in-situ or ex-situ relative tothe substrate.

As illustrated in FIG. 3A, the exposing of the substrate to the plasma(e.g., halogen-containing plasma) may be performed simultaneously withthe exposing the substrate to the oxygen-containing environment. Forexample, the process composition for forming plasma may include anoxygen-containing gas.

As illustrated in FIG. 3B, the exposing of the substrate to the plasma(e.g., halogen-containing plasma) may be performed sequentially with theexposing the substrate to the oxygen-containing environment. Forexample, the substrate may be exposed to the oxygen-containingenvironment and, thereafter, the substrate may be exposed to the plasma.Also, as shown in FIG. 3B, the exposing of the substrate to the plasmamay be performed sequentially and alternatingly with the exposing thesubstrate to the oxygen-containing environment for one or more exposurecycles. For example, the substrate may be exposed to theoxygen-containing environment and, thereafter, the substrate may beexposed to the plasma, thus, defining an exposure cycle, which may berepeated.

As illustrated in FIG. 3C, when performing both the exposing of thesubstrate to the plasma (e.g., halogen-containing plasma) and theexposing of the substrate to the oxygen-containing environment in theplasma processing system, the method may further include at least onepurging step for the plasma processing system inserted between theexposing the substrate to plasma and the exposing the substrate to theoxygen-containing environment.

According to another embodiment, a method for etching a metal-containinglayer on a substrate is illustrated in FIG. 4. As described in FIG. 4,the method comprises a flow chart 400 beginning in 410 with disposing asubstrate having both an aluminum-containing layer and a layercontaining Si and O formed thereon in a plasma processing system. Forexample, the aluminum-containing layer may include a bulk aluminum layerwith an aluminum oxide surface layer, and the layer containing Si and Omay include silicon oxide.

The method for etching may include, in 420, forming first plasma from aprocess composition containing HBr and an additive gas having thechemical formula C_(x)H_(y)R_(z), wherein R is a halogen element, x andy are equal to unity or greater, and z is equal to zero or greater, and,in 430, exposing the substrate to the first plasma to break through thealuminum oxide surface layer. Thereafter, the method may furtherinclude, in 440, forming second plasma from a process compositioncontaining HBr, and, in 450, exposing the substrate to the second plasmato etch the bulk aluminum.

According to yet another embodiment, when it is desirable to achieve atarget etch selectivity between etching the metal-containing layer, suchas the aluminum-containing layer, and another layer on the substrate,such as the layer containing Si and O (e.g., oxide layer 114 in FIGS. 1Band 1C), at least one of the process parameters noted above may bevaried. For example, the etch selectivity between aluminum oxide andsilicon oxide (i.e., the ratio of the aluminum oxide etch rate to thesilicon oxide etch rate) may be increased by decreasing or terminatingthe first RF power level for the electrical bias of the substrate (i.e.,zero-bias condition).

One or more of the methods for etching a metal-containing layerdescribed above may be performed utilizing a plasma processing systemsuch as the one described in FIG. 11. However, the methods discussed arenot to be limited in scope by this exemplary presentation. The method ofetching a metal-containing layer on a substrate according to variousembodiments described above may be performed in any one of the plasmaprocessing systems illustrated in FIGS. 5 through 11 and describedbelow.

According to one embodiment, a plasma processing system 500 configuredto perform the above identified process conditions is depicted in FIG. 5comprising a plasma processing chamber 510, substrate holder 520, uponwhich a substrate 525 to be processed is affixed, and vacuum pumpingsystem 550. Substrate 525 can be a semiconductor substrate, a wafer, aflat panel display, or a liquid crystal display. Plasma processingchamber 510 can be configured to facilitate the generation of plasma inplasma processing region 545 in the vicinity of a surface of substrate525. An ionizable gas or mixture of process gases is introduced via agas distribution system 540. For a given flow of process gas, theprocess pressure is adjusted using the vacuum pumping system 550. Plasmacan be utilized to create materials specific to a pre-determinedmaterials process, and/or to aid the removal of material from theexposed surfaces of substrate 525. The plasma processing system 500 canbe configured to process substrates of any desired size, such as 200 mmsubstrates, 300 mm substrates, or larger.

Substrate 525 can be affixed to the substrate holder 520 via a clampingsystem 528, such as a mechanical clamping system or an electricalclamping system (e.g., an electrostatic clamping system). Furthermore,substrate holder 520 can include a heating system (not shown) or acooling system (not shown) that is configured to adjust and/or controlthe temperature of substrate holder 520 and substrate 525. The heatingsystem or cooling system may comprise a re-circulating flow of heattransfer fluid that receives heat from substrate holder 520 andtransfers heat to a heat exchanger system (not shown) when cooling, ortransfers heat from the heat exchanger system to substrate holder 520when heating. In other embodiments, heating/cooling elements, such asresistive heating elements, or thermo-electric heaters/coolers can beincluded in the substrate holder 520, as well as the chamber wall of theplasma processing chamber 510 and any other component within the plasmaprocessing system 500.

Additionally, a heat transfer gas can be delivered to the backside ofsubstrate 525 via a backside gas supply system 526 in order to improvethe gas-gap thermal conductance between substrate 525 and substrateholder 520. Such a system can be utilized when temperature control ofthe substrate is required at elevated or reduced temperatures. Forexample, the backside gas supply system can comprise a two-zone gasdistribution system, wherein the helium gas-gap pressure can beindependently varied between the center and the edge of substrate 525.

In the embodiment shown in FIG. 5, substrate holder 520 can comprise anelectrode 522 through which RF power is coupled to the processing plasmain plasma processing region 545. For example, substrate holder 520 canbe electrically biased at a RF voltage via the transmission of RF powerfrom a RF generator 530 through an optional impedance match network 532to substrate holder 520. The RF electrical bias can serve to heatelectrons to form and maintain plasma. In this configuration, the systemcan operate as a reactive ion etch (RIE) reactor, wherein the chamberand an upper gas injection electrode serve as ground surfaces. A typicalfrequency for the RF bias can range from about 0.1 MHz to about 100 MHz.RF systems for plasma processing are well known to those skilled in theart.

Furthermore, the electrical bias of electrode 522 at a RF voltage may bepulsed using pulsed bias signal controller 531. The RF power output fromthe RF generator 530 may be pulsed between an off-state and an on-state,for example.

Alternately, RF power is applied to the substrate holder electrode atmultiple frequencies. Furthermore, impedance match network 532 canimprove the transfer of RF power to plasma in plasma processing chamber510 by reducing the reflected power. Match network topologies (e.g.L-type, π-type, T-type, etc.) and automatic control methods are wellknown to those skilled in the art.

Gas distribution system 540 may comprise a showerhead design forintroducing a mixture of process gases. Alternatively, gas distributionsystem 540 may comprise a multi-zone showerhead design for introducing amixture of process gases and adjusting the distribution of the mixtureof process gases above substrate 525. For example, the multi-zoneshowerhead design may be configured to adjust the process gas flow orcomposition to a substantially peripheral region above substrate 525relative to the amount of process gas flow or composition to asubstantially central region above substrate 525.

Vacuum pumping system 550 can include a turbo-molecular vacuum pump(TMP) capable of a pumping speed up to about 5000 liters per second (andgreater) and a gate valve for throttling the chamber pressure. Inconventional plasma processing devices utilized for dry plasma etching,a 1000 to 3000 liter per second TMP can be employed. TMPs are useful forlow pressure processing, typically less than about 50 mTorr. For highpressure processing (i.e., greater than about 100 mTorr), a mechanicalbooster pump and dry roughing pump can be used. Furthermore, a devicefor monitoring chamber pressure (not shown) can be coupled to the plasmaprocessing chamber 510.

Controller 555 comprises a microprocessor, memory, and a digital I/Oport capable of generating control voltages sufficient to communicateand activate inputs to plasma processing system 500 as well as monitoroutputs from plasma processing system 500. Moreover, controller 555 canbe coupled to and can exchange information with RF generator 530, pulsedbias signal controller 531, impedance match network 532, the gasdistribution system 540, vacuum pumping system 550, as well as thesubstrate heating/cooling system (not shown), the backside gas supplysystem 526, and/or the electrostatic clamping system 528. For example, aprogram stored in the memory can be utilized to activate the inputs tothe aforementioned components of plasma processing system 500 accordingto a process recipe in order to perform a plasma assisted process, suchas a plasma etch process, on substrate 525.

Controller 555 can be locally located relative to the plasma processingsystem 500, or it can be remotely located relative to the plasmaprocessing system 500. For example, controller 555 can exchange datawith plasma processing system 500 using a direct connection, anintranet, and/or the internet. Controller 555 can be coupled to anintranet at, for example, a customer site (i.e., a device maker, etc.),or it can be coupled to an intranet at, for example, a vendor site(i.e., an equipment manufacturer). Alternatively or additionally,controller 555 can be coupled to the internet. Furthermore, anothercomputer (i.e., controller, server, etc.) can access controller 555 toexchange data via a direct connection, an intranet, and/or the internet.

In the embodiment shown in FIG. 6, plasma processing system 600 can besimilar to the embodiment of FIG. 5 and further comprise either astationary, or mechanically or electrically rotating magnetic fieldsystem 660, in order to potentially increase plasma density and/orimprove plasma processing uniformity, in addition to those componentsdescribed with reference to FIG. 5. Moreover, controller 555 can becoupled to magnetic field system 660 in order to regulate the speed ofrotation and field strength. The design and implementation of a rotatingmagnetic field is well known to those skilled in the art.

In the embodiment shown in FIG. 7, plasma processing system 700 can besimilar to the embodiment of FIG. 5 or FIG. 6, and can further comprisean upper electrode 770 to which RF power can be coupled from RFgenerator 772 through optional impedance match network 774. A frequencyfor the application of RF power to the upper electrode can range fromabout 0.1 MHz to about 200 MHz. Additionally, a frequency for theapplication of power to the lower electrode can range from about 0.1 MHzto about 100 MHz. Moreover, controller 555 is coupled to RF generator772 and impedance match network 774 in order to control the applicationof RF power to upper electrode 770. The design and implementation of anupper electrode is well known to those skilled in the art. The upperelectrode 770 and the gas distribution system 540 can be designed withinthe same chamber assembly, as shown. Alternatively, upper electrode 770may comprise a multi-zone electrode design for adjusting the RF powerdistribution coupled to plasma above substrate 525. For example, theupper electrode 770 may be segmented into a center electrode and an edgeelectrode.

In the embodiment shown in FIG. 8, plasma processing system 800 can besimilar to the embodiment of FIG. 7, and can further comprise a directcurrent (DC) power supply 890 coupled to the upper electrode 770opposing substrate 525. The upper electrode 770 may comprise anelectrode plate. The electrode plate may comprise a silicon-containingelectrode plate. Moreover, the electrode plate may comprise a dopedsilicon electrode plate. The DC power supply 890 can include a variableDC power supply. Additionally, the DC power supply 890 can include abipolar DC power supply. The DC power supply 890 can further include asystem configured to perform at least one of monitoring, adjusting, orcontrolling the polarity, current, voltage, or on/off state of the DCpower supply 890. Once plasma is formed, the DC power supply 890facilitates the formation of a ballistic electron beam. An electricalfilter (not shown) may be utilized to de-couple RF power from the DCpower supply 890.

For example, the DC voltage applied to upper electrode 770 by DC powersupply 890 may range from approximately −2000 volts (V) to approximately1000 V. Desirably, the absolute value of the DC voltage has a valueequal to or greater than approximately 100 V, and more desirably, theabsolute value of the DC voltage has a value equal to or greater thanapproximately 500 V. Additionally, it is desirable that the DC voltagehas a negative polarity. Furthermore, it is desirable that the DCvoltage is a negative voltage having an absolute value greater than theself-bias voltage generated on a surface of the upper electrode 770. Thesurface of the upper electrode 770 facing the substrate holder 520 maybe comprised of a silicon-containing material.

In the embodiment shown in FIG. 9, plasma processing system 900 can besimilar to the embodiments of FIGS. 5 and 6, and can further comprise aninductive coil 980 to which RF power is coupled via RF generator 982through optional impedance match network 984. RF power is inductivelycoupled from inductive coil 980 through a dielectric window (not shown)to plasma processing region 545. A frequency for the application of RFpower to the inductive coil 980 can range from about 10 MHz to about 100MHz. Similarly, a frequency for the application of power to the chuckelectrode can range from about 0.1 MHz to about 100 MHz. In addition, aslotted Faraday shield (not shown) can be employed to reduce capacitivecoupling between the inductive coil 980 and plasma in the plasmaprocessing region 545. Moreover, controller 555 can be coupled to RFgenerator 982 and impedance match network 984 in order to control theapplication of power to inductive coil 980.

In an alternate embodiment, as shown in FIG. 10, plasma processingsystem 1000 can be similar to the embodiment of FIG. 9, and can furthercomprise an inductive coil 1080 that is a “spiral” coil or “pancake”coil in communication with the plasma processing region 545 from aboveas in a transformer coupled plasma (TCP) reactor. The design andimplementation of an inductively coupled plasma (ICP) source, ortransformer coupled plasma (TCP) source, is well known to those skilledin the art.

Alternately, plasma can be formed using electron cyclotron resonance(ECR). In yet another embodiment, the plasma is formed from thelaunching of a Helicon wave. In yet another embodiment, the plasma isformed from a propagating surface wave. Each plasma source describedabove is well known to those skilled in the art.

In the embodiment shown in FIG. 11, plasma processing system 1100 can besimilar to the embodiment of FIG. 5, and can further comprise a surfacewave plasma (SWP) source 1130. The SWP source 1130 can comprise a slotantenna, such as a radial line slot antenna (RLSA), to which microwavepower is coupled via a power coupling system 1190.

Referring now to FIG. 12, a schematic representation of a SWP source1230 is provided according to an embodiment. The SWP source 1230comprises an electromagnetic (EM) wave launcher 1232 configured tocouple EM energy in a desired EM wave mode to a plasma by generating asurface wave on a plasma surface 1260 of the EM wave launcher 1232adjacent plasma. Furthermore, the SWP source 1230 comprises a powercoupling system 1290 coupled to the EM wave launcher 1232, andconfigured to provide the EM energy to the EM wave launcher 1232 forforming the plasma.

The EM wave launcher 1232 includes a microwave launcher configured toradiate microwave power into plasma processing region 545 (see FIG. 11).The EM wave launcher 1232 is coupled to the power coupling system 1290via coaxial feed 1238 through which microwave energy is transferred. Thepower coupling system 1290 includes a microwave source 1292, such as a2.45 GHz microwave power source. Microwave energy generated by themicrowave source 1292 is guided through a waveguide 1294 to an isolator1296 for absorbing microwave energy reflected back to the microwavesource 1292. Thereafter, the microwave energy is converted to a coaxialTEM (transverse electromagnetic) mode via a coaxial converter 1298.

A tuner may be employed for impedance matching, and improved powertransfer. The microwave energy is coupled to the EM wave launcher 1232via the coaxial feed 1238, wherein another mode change occurs from theTEM mode in the coaxial feed 1238 to a TM (transverse magnetic) mode.Additional details regarding the design of the coaxial feed 1238 and theEM wave launcher 1232 can be found in U.S. Pat. No. 5,024,716, entitled“Plasma processing apparatus for etching, ashing, and film-formation”;the content of which is herein incorporated by reference in itsentirety.

Referring now to FIGS. 13A and 13B, a schematic cross-sectional view anda bottom view, respectively, of an EM wave launcher 1332 are providedaccording to one embodiment. The EM wave launcher 1332 comprises acoaxial feed 1338 having an inner conductor 1340, an outer conductor1342, and insulator 1341, such as an air gap, and a slot antenna 1346having a plurality of slots 1348 coupled between the inner conductor1340 and the outer conductor 1342 as shown in FIG. 13A. The plurality ofslots 1348 permits the coupling of EM energy from a first region abovethe slot antenna 1346 to a second region below the slot antenna 1346,wherein plasma is formed adjacent a plasma surface 1360 on the EM wavelauncher 1332. The EM wave launcher 1332 may further comprise a slowwave plate 1344, and a resonator plate 1350.

The number, geometry, size, and distribution of the slots 1348 are allfactors that can contribute to the spatial uniformity of the plasmaformed in the plasma processing region 545 (see FIG. 11). Thus, thedesign of the slot antenna 1346 may be used to control the spatialuniformity of the plasma in the plasma processing region 545 (see FIG.11).

As shown in FIG. 13A, the EM wave launcher 1332 may comprise a fluidchannel 1356 that is configured to flow a temperature control fluid fortemperature control of the EM wave launcher 1332. Although not shown,the EM wave launcher 1332 may further be configured to introduce aprocess gas through the plasma surface 1360 to the plasma. Although notshown, a gas distribution system, such as the gas distribution system(540) of FIG. 11, may be connected to the EM wave launcher 1332 and/orthe chamber wall 1352 for introducing a process gas into the processchamber.

Referring still to FIG. 13A, the EM wave launcher 1332 may be coupled toan upper chamber portion of a plasma processing system, wherein a vacuumseal can be formed between an upper chamber wall 1352 and the EM wavelauncher 1332 using a sealing device 1354. The sealing device 1354 caninclude an elastomer O-ring; however, other known sealing mechanisms maybe used.

In general, the inner conductor 1340 and the outer conductor 1342 of thecoaxial feed 1338 comprise a conductive material, such as a metal, whilethe slow wave plate 1344 and the resonator plate 1350 comprise adielectric material. In the latter, the slow wave plate 1344 and theresonator plate 1350 preferably comprise the same material; however,different materials may be used. The material selected for fabricationof the slow wave plate 1344 is chosen to reduce the wavelength of thepropagating electromagnetic (EM) wave relative to the correspondingfree-space wavelength, and the dimensions of the slow wave plate 1344and the resonator plate 1350 are chosen to ensure the formation of astanding wave effective for radiating EM energy into the plasmaprocessing region 545 (see FIG. 11).

The slow wave plate 1344 and the resonator plate 1350 can be fabricatedfrom a dielectric material, including silicon-containing materials suchas quartz (silicon dioxide), or a high dielectric constant (high-k)materials. For example, the high-k material may possess a dielectricconstant greater than a value of 4. In particular, when the plasmaprocessing system is utilized for etch process applications, quartz isoften chosen for compatibility with the etch process.

For example, the high-k material can include intrinsic crystal silicon,alumina ceramic, aluminum nitride, and sapphire. However, other high-kmaterials may be used. Moreover, a particular high-k material may beselected in accordance with the parameters of a particular process. Forexample, when the resonator plate 1350 is fabricated from intrinsiccrystal silicon, the plasma frequency exceeds 2.45 GHz at a temperatureof 45 degrees C. Therefore, intrinsic crystal silicon is appropriate forlow temperature processes (i.e., less than 45 degrees C.). For highertemperature processes, the resonator plate 1350 can be fabricated fromalumina (Al₂O₃), or sapphire.

Plasma uniformity and plasma stability may remain as challenges for thepractical implementation of a SWP source as described above. In thelatter, the standing wave at the resonator plate-plasma interface, i.e.,at the plasma surface 1360, may be prone to mode jumps as plasmaparameters shift.

As shown in FIGS. 13A and 13B, the EM wave launcher 1332 may befabricated with a first recess configuration 1362 formed in the plasmasurface 1360 and optionally a second recess configuration 1364 formed inthe plasma surface 1360 according to one embodiment.

The first recess configuration 1362 may comprise a first plurality ofrecesses. Each recess in the first recess configuration 1362 maycomprise a unique indentation or dimple formed within the plasma surface1360. For example, a recess in the first recess configuration 1362 maycomprise a cylindrical geometry, a conical geometry, a frusto-conicalgeometry, a spherical geometry, an aspherical geometry, a rectangulargeometry, a pyramidal geometry, or any arbitrary shape. The first recessdistribution 1362 may comprise recesses characterized by a first size(e.g., latitudinal dimension (or width), and/or longitudinal dimension(or depth)).

The second recess configuration 1364 may comprise a plurality ofrecesses. Each recess in the second recess configuration 1364 maycomprise a unique indentation or dimple formed within the plasma surface1360. For example, a recess in the second recess configuration 1364 maycomprise a cylindrical geometry, a conical geometry, a frusto-conicalgeometry, a spherical geometry, an aspherical geometry, a rectangulargeometry, a pyramidal geometry, or any arbitrary shape. The secondrecess distribution 1364 may comprise recesses characterized by a secondsize (e.g., latitudinal dimension (or width), and/or longitudinaldimension (or depth)). The first size of the recesses in the firstrecess configuration 1362 may or may not be the same as the second sizeof the recesses in the second recess configuration 1364. For instance,the second size may be smaller than the first size.

As shown in FIGS. 13A and 13B, the resonator plate 1350 comprises adielectric plate having a plate diameter and a plate thickness. Therein,the plasma surface 1360 on resonator plate 1350 comprises a planarsurface 1366 within which the first recess configuration 1362 and thesecond recess configuration 1364 are formed. Alternatively, theresonator plate 1350 comprises a non-planar geometry or an arbitrarygeometry. Therein, the plasma surface 1360 may comprise a non-planarsurface within which the first recess configuration and the secondrecess configuration are formed (not shown). For example, the non-planarsurface may be concave, or convex, or a combination thereof.

The propagation of EM energy in the resonator plate 1350 may becharacterized by an effective wavelength (λ) for a given frequency of EMenergy and dielectric constant for the resonator plate 1350. The platethickness may be an integer number of quarter wavelengths (n λ/4, wheren is an integer greater than zero) or an integer number of halfwavelengths (m λ/2, where m is an integer greater than zero). Forinstance, the plate thickness may be about half the effective wavelength(λ/2) or greater than half the effective wavelength (>λ/2).Alternatively, the plate thickness may be a non-integral fraction of theeffective wavelength (i.e., not an integral number of half or quarterwavelengths). Alternatively yet, the plate thickness may range fromabout 25 mm (millimeters) to about 45 mm.

As an example, the first recess configuration 1362 may comprise a firstplurality of cylindrical recesses, wherein each of the first pluralityof cylindrical recesses is characterized by a first depth and a firstdiameter. As shown in FIG. 13B, the first recess configuration 1362 islocated near an outer region of the plasma surface 1360.

The first diameter may be an integer number of quarter wavelengths (nλ/4, where n is an integer greater than zero), or an integer number ofhalf wavelengths (m λ/2, where m is an integer greater than zero), or anon-integral fraction of the effective wavelength. Additionally, a firstdifference between the plate thickness and the first depth may be aninteger number of quarter wavelengths (n λ/4, where n is an integergreater than zero), or an integer number of half wavelengths (m λ/2,where m is an integer greater than zero), or a non-integral fraction ofthe effective wavelength. For instance, the first diameter may be abouthalf the effective wavelength (λ/2), and the first difference betweenthe plate thickness and the first depth may be about half the effectivewavelength (λ/2) or about quarter the effective wavelength (λ/4).Additionally, for instance, the plate thickness may be about half theeffective wavelength (λ/2) or greater than half the effective wavelength(>λ/2).

Alternatively, the first diameter may range from about 25 mm to about 35mm, and the first difference between the plate thickness and the firstdepth may range from about 10 mm to about 35 mm. Alternatively yet, thefirst diameter may range from about 30 mm to about 35 mm, and the firstdifference may range from about 10 mm to about 20 mm. Alternatively yet,the first diameter and/or first depth may be a fraction of the platethickness.

In the first recess configuration 1362, chamfers, rounds and/or fillets(i.e., surface/corner radius or bevel) may be utilized to affect smoothsurface transitions between adjacent surfaces. In a cylindrical recess,a surface radius may be disposed at the corner between the cylindricalsidewall and the bottom of the recess. Additionally, in a cylindricalrecess, a surface radius may be disposed at the corner between thecylindrical sidewall and the plasma surface 1360. For example, thesurface radius may range from about 1 mm to about 3 mm.

As another example, the second recess configuration 1364 may comprise asecond plurality of cylindrical recesses, each of the second pluralityof cylindrical recesses being characterized by a second depth and asecond diameter. As shown in FIG. 13B, the second recess configuration1364 is located near an inner region of the plasma surface 1360.

The second diameter may be an integer number of quarter wavelengths (nλ/4, where n is an integer greater than zero), or an integer number ofhalf wavelengths (m λ/2, where m is an integer greater than zero), or anon-integral fraction of the effective wavelength. Additionally, asecond difference between the plate thickness and the second depth maybe an integer number of quarter wavelengths (n λ/4, where n is aninteger greater than zero), or an integer number of half wavelengths (mλ/2, where m is an integer greater than zero), or a non-integralfraction of the effective wavelength. For instance, the second diametermay be about half the effective wavelength (λ/2), and the seconddifference between the plate thickness and the second depth may be abouthalf the effective wavelength (λ/2) or about quarter the effectivewavelength (λ/4). Additionally, for instance, the plate thickness may beabout half the effective wavelength (λ/2) or greater than half theeffective wavelength (>λ/2).

Alternatively, the second diameter may range from about 25 mm to about35 mm, and the second difference between the plate thickness and thesecond depth may range from about 10 mm to about 35 mm. Alternativelyyet, the second diameter may range from about 30 mm to about 35 mm, andthe second difference may range from about 10 mm to about 20 mm.Alternatively yet, the second diameter and/or second depth may be afraction of the plate thickness.

In the second recess configuration 1364, chamfers, rounds and/or fillets(i.e., surface/corner radius or bevel) may be utilized to affect smoothsurface transitions between adjacent surfaces. In a cylindrical recess,a surface radius may be disposed at the corner between the cylindricalsidewall and the bottom of the recess. Additionally, in a cylindricalrecess, a surface radius may be disposed at the corner between thecylindrical sidewall and the plasma surface 1360. For example, thesurface radius may range from about 1 mm to about 3 mm.

Referring again to FIG. 13B, a bottom view of the EM wave launcher 1332depicted in FIG. 13A is provided. The plurality of slots 1348 in slotantenna 1346 are illustrated as if one can see through resonator plate1350 to the slot antenna 1346. As shown in FIG. 13B, the plurality ofslots 1348 may be arranged in pairs, wherein each of the pair of slotscomprises a first slot oriented orthogonal to a second slot. However,the orientation of slots in the plurality of slots 1348 may bearbitrary. For example, the orientation of slots in the plurality ofslots 1348 may be according to a pre-determined pattern for plasmauniformity and/or plasma stability.

The first recess configuration 1362 is substantially aligned with afirst arrangement of slots in the plurality of slots 1348. Therein, atleast one recess of the first recess configuration 1362 may be aligned,partially aligned, or not aligned with one or more of the plurality ofslots 1348. The second recess configuration 1364 is either partlyaligned with a second arrangement of slots in the plurality of slots1348 or not aligned with the second arrangement of slots in theplurality of slots 1348. As shown in FIG. 13B, the second recessconfiguration 1364 is not aligned with the second arrangement of slotsin the plurality of slots 1348.

As a consequence, the arrangement of the first and second recessconfigurations 1362, 1364 and their alignment with one or more of theplurality of slots 1348 may be optimized to control and/or improveplasma uniformity and/or stability. Additional details regarding thedesign of the plasma surface 1360 and the EM wave launcher 1332 can befound in pending U.S. Patent Application Publication Serial No.2011/0057562, entitled “Stable surface wave plasma source”, and filed onSep. 8, 2009; the content of which is herein incorporated by referencein its entirety.

Referring now to FIG. 14, a schematic cross-sectional view of an EM wavelauncher 1432 is provided according to another embodiment. The EM wavelauncher 1432 comprises the coaxial feed 1438 having an inner conductor1440, an outer conductor 1442, and insulator 1441, such as an air gap,and a slot antenna 1446 having a plurality of slots 1448 coupled betweenthe inner conductor 1440 and the outer conductor 1442 as shown in FIG.14. The plurality of slots 1448 permits the coupling of EM energy from afirst region above the slot antenna 1446 to a second region below theslot antenna 1446, wherein plasma is formed adjacent a plasma surface1460 on the EM wave launcher 1432. The EM wave launcher 1432 may furthercomprise a slow wave plate 1444, and a resonator plate 1450.

The number, geometry, size, and distribution of the slots 1448 are allfactors that can contribute to the spatial uniformity of the plasmaformed in the plasma processing region 545 (see FIG. 11). Thus, thedesign of the slot antenna 1446 may be used to control the spatialuniformity of the plasma in the plasma processing region 545 (see FIG.11).

As shown in FIG. 14, the EM wave launcher 1432 may comprise a fluidchannel 1456 that is configured to flow a temperature control fluid fortemperature control of the EM wave launcher 1432. Although not shown, agas distribution system, such as the gas distribution system (540) ofFIG. 11, may be connected to the EM wave launcher 1432 and/or thechamber wall 1452 for introducing a process gas into the processchamber.

Referring still to FIG. 14, the EM wave launcher 1432 may be coupled toan upper chamber portion of a plasma processing system, wherein a vacuumseal can be formed between an upper chamber wall 1452 and the EM wavelauncher 1432 using a sealing device 1454. The sealing device 1454 caninclude an elastomer O-ring; however, other known sealing mechanisms maybe used.

In general, the inner conductor 1440 and the outer conductor 1442 of thecoaxial feed 1438 comprise a conductive material, such as a metal, whilethe slow wave plate 1444 and the resonator plate 1450 comprise adielectric material. In the latter, the slow wave plate 1444 and theresonator plate 1450 preferably comprise the same material; however,different materials may be used. The material selected for fabricationof the slow wave plate 1444 is chosen to reduce the wavelength of thepropagating electromagnetic (EM) wave relative to the correspondingfree-space wavelength, and the dimensions of the slow wave plate 1444and the resonator plate 1450 are chosen to ensure the formation of astanding wave effective for radiating EM energy into the plasmaprocessing region 545 (see FIG. 11).

The slow wave plate 1444 and the resonator plate 1450 can be fabricatedfrom a dielectric material, including silicon-containing materials suchas quartz (silicon dioxide), or a high dielectric constant (high-k)materials. For example, the high-k material may possess a dielectricconstant greater than a value of 4. In particular, when the plasmaprocessing system is utilized for etch process applications, quartz isoften chosen for compatibility with the etch process.

For example, the high-k material can include intrinsic crystal silicon,alumina ceramic, aluminum nitride, and sapphire. However, other high-kmaterials may be used. Moreover, a particular high-k material may beselected in accordance with the parameters of a particular process. Forexample, when the resonator plate 1450 is fabricated from intrinsiccrystal silicon, the plasma frequency exceeds 2.45 GHz at a temperatureof 45 degrees C. Therefore, intrinsic crystal silicon is appropriate forlow temperature processes (i.e., less than 45 degrees C.). For highertemperature processes, the resonator plate 1450 can be fabricated fromalumina (Al₂O₃), or sapphire.

Plasma uniformity and plasma stability may remain as challenges for thepractical implementation of a SWP source as described above. In thelatter, the standing wave at the resonator plate-plasma interface, i.e.,at the plasma surface 1460, may be prone to mode jumps as plasmaparameters shift.

As shown in FIG. 14, the EM wave launcher 1432 may be fabricated with afirst recess configuration 1462 formed in the plasma surface 1460 andoptionally a second recess configuration 1464 formed in the plasmasurface 1460 according to one embodiment.

The first recess configuration 1462 may comprise a first channel recess.For example, the first channel recess in the first recess configuration1462 may include a cross-section that has a frusto-conical geometry.However, other geometries may be used, e.g., a spherical geometry, anaspherical geometry, a rectangular geometry, a pyramidal geometry, orany arbitrary shape. The first recess distribution 1462 may comprise achannel recess characterized by a first size (e.g., latitudinaldimension (or width), and/or longitudinal dimension (or depth)).

The second recess configuration 1464 may comprise a second channelrecess. For example, the second channel recess in the second recessconfiguration 1464 may include a cross-section that has a frusto-conicalgeometry. However, other geometries may be used, e.g., a sphericalgeometry, an aspherical geometry, a rectangular geometry, a pyramidalgeometry, or any arbitrary shape. The second recess distribution 1464may comprise a channel recess characterized by a second size (e.g.,latitudinal dimension (or width), and/or longitudinal dimension (ordepth)). The first size of the first channel recess in the first recessconfiguration 1462 may or may not be the same as the second size of thesecond channel recess in the second recess configuration 1464. Forinstance, the second size may be larger than the first size.

As shown in FIG. 14, the resonator plate 1450 comprises a dielectricplate having a plate diameter and a plate thickness. Therein, the plasmasurface 1460 on resonator plate 1450 comprises a planar surface 1466within which the first recess configuration 1462 and the second recessconfiguration 1464 are formed. Alternatively, the resonator plate 1450comprises a non-planar geometry or an arbitrary geometry. Therein, theplasma surface 1460 may comprise a non-planar surface within which thefirst recess configuration and the second recess configuration areformed (not shown). For example, the non-planar surface may be concave,or convex, or a combination thereof.

The arrangement of the first and second recess configurations (1462,1464) and their alignment with one or more of the plurality of slots1448 may be optimized to control and/or improve plasma uniformity and/orstability. Additional details regarding the design of the plasma surface1460 and the EM wave launcher 1432 can be found in pending U.S. patentapplication Ser. No. 10/570,631, entitled “Plasma processing equipment”,filed on Dec. 19, 2006, and published as U.S. Patent ApplicationPublication No. 2007/0113788A1; the content of which is hereinincorporated by reference in its entirety.

Although only certain embodiments of this invention have been describedin detail above, those skilled in the art will readily appreciate thatmany modifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of this invention.Accordingly, all such modifications are intended to be included withinthe scope of this invention.

The invention claimed is:
 1. A method for etching a metal-containinglayer on a substrate, comprising: disposing a substrate having analuminum-containing layer formed thereon in a plasma processing system;forming plasma from a process composition containing a halogen element;exposing said substrate to said plasma to etch said aluminum-containinglayer while simultaneously exposing said substrate to anoxygen-containing environment to oxidize a surface of saidaluminum-containing layer and control an etch rate of saidaluminum-containing layer.
 2. The method of claim 1, wherein saidaluminum-containing layer is aluminum or aluminum oxide (AlO_(x)). 3.The method of claim 1, wherein said process composition contains afluorine-containing gas, a chlorine-containing gas, a bromine-containinggas, a hydrogen halide gas, or a halomethane gas, or any combination oftwo or more thereof.
 4. The method of claim 1, wherein said processcomposition contains Br and one or more elements selected from a groupconsisting of C, H, F, and Cl.
 5. The method of claim 1, wherein saidprocess composition contains C and one or more elements selected from agroup consisting of H, F, Cl, Br, and I.
 6. The method of claim 1,wherein said process composition further contains an additive gas havinga chemical formula C_(x)H_(y)R_(z), where R is a halogen element, x andy are equal to unity or greater, and z is equal to zero or greater. 7.The method of claim 1, wherein said process composition contains HBr andan additive gas having a chemical formula C_(x)H_(y)F_(z), where x, yand z are equal to unity or greater.
 8. The method of claim 1, whereinsaid process composition contains HBr, CH₃F, and optionally Ar.
 9. Themethod of claim 1, wherein said oxygen-containing environment containsO, O₂, O₃, CO, CO₂, NO, N₂O, or NO₂, or any combination of two or morethereof.
 10. The method of claim 1, wherein said oxygen-containingenvironment contains an oxygen-containing plasma.
 11. The method ofclaim 1, further comprising: applying an electrical bias to saidsubstrate by coupling radio frequency (RF) power to a substrate holderupon which said substrate rests; and achieving a target etch selectivitybetween said aluminum-containing layer and a layer containing Si and Oformed on said substrate by adjusting an RF power level for saidelectrical bias.
 12. The method of claim 1, wherein said forming plasmacomprises coupling electromagnetic (EM) energy at a microwave frequencyin a desired EM wave mode to said plasma by generating a surface wave ona plasma surface of an EM wave launcher adjacent said plasma, said EMwave launcher comprises a slot antenna having a plurality of slotsformed there through configured to couple said EM energy from a firstregion above said slot antenna to a second region below said slotantenna.
 13. A method for etching a metal-containing layer on asubstrate, comprising: disposing a substrate having analuminum-containing layer formed thereon in a plasma processing system;etching said aluminum-containing layer in a two-step etching process,comprising: forming first plasma from a first process compositioncontaining HBr and an additive gas having a chemical formulaC_(x)H_(y)R_(z), wherein R is a halogen element, x and y are equal tounity or greater, and z is equal to zero or greater, and exposing saidsubstrate to said first plasma to etch said aluminum-containing layer;and thereafter, forming second plasma from a second process compositioncontaining HBr, and exposing said substrate to said second plasma tofurther etch said aluminum-containing layer.
 14. The method of claim 13,wherein said aluminum-containing layer includes a bulk aluminum layerwith an aluminum oxide (AlO_(x)) surface layer, and wherein said firstplasma etches the aluminum oxide surface layer and the second plasmaetches said bulk aluminum layer.
 15. The method of claim 14, whereinsaid additive gas is CH₃F.